This invention relates to thickeners for aqueous systems based upon polyethers. More specifically this invention relates to thickeners for aqueous systems, particularly aqueous pesticide systems and latex paint systems.
Polymeric water soluble thickening agents are widely used for many purposes. Commercially available polymeric thickeners differ widely in chemical composition. The diversity of available thickening agents is an indication that not all are equally useful. It is not unusual to find some thickening agents which perform well in a certain environment and not at all in another environment. In fact, in some uses, no one thickening agent is completely satisfactory and there is a continual need and a continuing search for new thickening agents to satisfy many unmet needs. For instance, various cellulose derivatives or other water soluble polymers such as sodium polyacrylates, polyacrylamides and polyethylene glycol fatty acid diesters are representative thickening agents. The polyethylene glycol fatty acid diesters are widely used for textile printing emulsions, cosmetic emulsions, and aqueous pigment suspensions. Polyoxyalkylene compounds including high molecular weight materials are well known for use as surface active agents as disclosed in U.S. Patent 2,674,619.
Current technology for the preparation of aqueous dispersions of pesticides requires the inclusion of a thickener, the most successful of which at present appear to be the use of a vegetable gum or inorganic thickener to increase the viscosity (or viscous yield strength) of the formulation.
The polyoxyalkylene compounds of the type disclosed in U.S. Pat. No. 2,674,619 are useful as thickeners only with those having the highest molecular weights reasonably obtainable under commercial conditions. Because high molecular weight polyethers require a disproportionately longer processing time to produce, it would be desirable to prepare high efficiency thickeners utilizing low molecular weight polymers.
In U.S. Pat. No. 3,538,033 there are disclosed polyoxyalkylene derivatives of diepoxide having thickener properties. The thickener compositions disclosed are useful for thickening aqueous systems and are prepared by reacting a diepoxide compound having at least 12 carbon atoms with an alkylene oxide adduct containing from 100 to 250 moles of ethylene oxide units.
Polyoxyalkylene type thickeners are also disclosed in U.S. Pat. No. 4,354,956 and U.S. Pat. No. 4,288,639.
Pesticide compositions incorporating nonionic surfactants including oxyalkylene polymers and copolymers, particularly oxyethylene/oxypropylene copolymers, are disclosed in U.S. Pat. Nos. 4,351,753; 4,434,078; and 4,434,077.
Also the preparation of latex paints requires the use of a thickener.